Ether carboxylates, which have a high stability in hard water, a good detergency, an excellent environmental suitability such as good biodegradability and low fish toxicity, and a low skin irritation, are surfactants useful for use in skin care products such as shampoos, body cleansers and creams, dish washing detergents, bathroom and bathtub detergents, and house detergents.
Such an ether carboxylate is generally produced from an ether alcohol obtained by reacting an alcohol with an alkylene oxide in the presence of an alkali catalyst, followed by neutralization with acetic acid. More specifically, the ether alcohol is reacted with a monohalogenoacetic acid or its salt in the presence of an alkali metal hydroxide according to Williamson ether synthesis.
However, the ether carboxylate produced by the above method has an off-odor and is not satisfactorily used for products directly applied to human bodies such as shampoos and facial cleansers.
Patent Document 1 discloses a process for producing an ether carboxylate in which an aliphatic monohydric alcohol is reacted with an alkylene oxide in the presence of a quaternary ammonium salt to obtain an ether alcohol, and then the thus obtained ether alcohol is reacted with a monohalogenoacetic acid (or its salt) and an alkali metal hydroxide.
Patent Document 2 discloses a process for producing an ether carboxylate in which an aliphatic monohydric alcohol or its alkylene oxide adduct (ether alcohol) is reacted with a monohalogenated lower carboxylic acid salt and an alkali metal hydroxide in the form of beads while removing water under reduced pressure, if required, in the presence of a solvent.
Patent Document 3 discloses a process for producing an alkali salt of a carboxylic acid in which a terminal aliphatic monohydric alcohol of a polyoxyethylene chain-containing ether-type nonionic surfactant is oxidized with oxygen in the presence of a palladium catalyst.
However, Patent Documents 1 to 3 do not disclose nor suggest a method for improving an odor of the product.
Patent Document 4 discloses an ether alcohol which is stabilized by incorporation of lactic acid (or its salt) into an ether alcohol obtained by reaction of an aliphatic primary alcohol with ethylene oxide and which shows a less change in carbonyl value, acid value, pH, sulfuric acid wash color and odor. However, Patent Document 4 does not disclose nor suggest improvement of the odor of an ether carboxylate obtained using the ether alcohol as a raw material.    Patent Document 1: JP 08-283196A    Patent Document 2: JP 2000-154163A    Patent Document 3: JP 53-141218A    Patent Document 4: JP 61-183241A